[PATCH] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()

[PATCH] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()

[Jiaming Zhang]

The ethtool tsconfig Netlink path can trigger a null pointer
dereference. A call chain such as:

  tsconfig_prepare_data() ->
  dev_get_hwtstamp_phylib() ->
  vlan_hwtstamp_get() ->
  generic_hwtstamp_get_lower() ->
  generic_hwtstamp_ioctl_lower()

results in generic_hwtstamp_ioctl_lower() being called with
kernel_cfg->ifr as NULL.

The generic_hwtstamp_ioctl_lower() function does not expect a
NULL ifr and dereferences it, leading to a system crash.

Fix this by adding a NULL check for kernel_cfg->ifr in
generic_hwtstamp_get/set_lower(). If ifr is NULL, return
-EOPNOTSUPP to prevent the call to the legacy IOCTL helper.

Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to get/set hwtstamp config")
Closes: https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3
Signed-off-by: Jiaming Zhang <r772577952@gmail.com>
---
 net/core/dev_ioctl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index ad54b12d4b4c..39eaf6ba981a 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -474,6 +474,10 @@ int generic_hwtstamp_get_lower(struct net_device *dev,
 		return err;
 	}
 
+	/* Netlink path with unconverted driver */
+	if (!kernel_cfg->ifr)
+		return -EOPNOTSUPP;
+
 	/* Legacy path: unconverted lower driver */
 	return generic_hwtstamp_ioctl_lower(dev, SIOCGHWTSTAMP, kernel_cfg);
 }
@@ -498,6 +502,10 @@ int generic_hwtstamp_set_lower(struct net_device *dev,
 		return err;
 	}
 
+	/* Netlink path with unconverted driver */
+	if (!kernel_cfg->ifr)
+		return -EOPNOTSUPP;
+
 	/* Legacy path: unconverted lower driver */
 	return generic_hwtstamp_ioctl_lower(dev, SIOCSHWTSTAMP, kernel_cfg);
 }
-- 
2.34.1

Re: [PATCH] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()

[kernel test robot]

Hi,

Thanks for your patch.

FYI: kernel test robot notices the stable kernel rule is not satisfied.

The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#option-1

Rule: add the tag "Cc: stable@vger.kernel.org" in the sign-off area to have the patch automatically included in the stable tree.
Subject: [PATCH] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Link: https://lore.kernel.org/stable/20251030093621.3563440-1-r772577952%40gmail.com

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()

[Kory Maincent]

On Thu, 30 Oct 2025 09:36:21 +0000
Jiaming Zhang <r772577952@gmail.com> wrote:

> The ethtool tsconfig Netlink path can trigger a null pointer
> dereference. A call chain such as:
> 
>   tsconfig_prepare_data() ->
>   dev_get_hwtstamp_phylib() ->
>   vlan_hwtstamp_get() ->
>   generic_hwtstamp_get_lower() ->
>   generic_hwtstamp_ioctl_lower()
> 
> results in generic_hwtstamp_ioctl_lower() being called with
> kernel_cfg->ifr as NULL.
> 
> The generic_hwtstamp_ioctl_lower() function does not expect a
> NULL ifr and dereferences it, leading to a system crash.
> 
> Fix this by adding a NULL check for kernel_cfg->ifr in
> generic_hwtstamp_get/set_lower(). If ifr is NULL, return
> -EOPNOTSUPP to prevent the call to the legacy IOCTL helper.
> 
> Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to
> get/set hwtstamp config") Closes:
> https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3
> Signed-off-by: Jiaming Zhang <r772577952@gmail.com> ---
>  net/core/dev_ioctl.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
> index ad54b12d4b4c..39eaf6ba981a 100644
> --- a/net/core/dev_ioctl.c
> +++ b/net/core/dev_ioctl.c
> @@ -474,6 +474,10 @@ int generic_hwtstamp_get_lower(struct net_device *dev,
>  		return err;
>  	}
>  
> +	/* Netlink path with unconverted driver */

nit: "lower driver", to be precise.

With this change:
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>

Thank you!

> +	if (!kernel_cfg->ifr)
> +		return -EOPNOTSUPP;
> +
>  	/* Legacy path: unconverted lower driver */
>  	return generic_hwtstamp_ioctl_lower(dev, SIOCGHWTSTAMP, kernel_cfg);
>  }
> @@ -498,6 +502,10 @@ int generic_hwtstamp_set_lower(struct net_device *dev,
>  		return err;
>  	}
>  
> +	/* Netlink path with unconverted driver */

same.

> +	if (!kernel_cfg->ifr)
> +		return -EOPNOTSUPP;
> +
>  	/* Legacy path: unconverted lower driver */
>  	return generic_hwtstamp_ioctl_lower(dev, SIOCSHWTSTAMP, kernel_cfg);
>  }



-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

[PATCH v2] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()

[Jiaming Zhang]

The ethtool tsconfig Netlink path can trigger a null pointer
dereference. A call chain such as:

  tsconfig_prepare_data() ->
  dev_get_hwtstamp_phylib() ->
  vlan_hwtstamp_get() ->
  generic_hwtstamp_get_lower() ->
  generic_hwtstamp_ioctl_lower()

results in generic_hwtstamp_ioctl_lower() being called with
kernel_cfg->ifr as NULL.

The generic_hwtstamp_ioctl_lower() function does not expect a
NULL ifr and dereferences it, leading to a system crash.

Fix this by adding a NULL check for kernel_cfg->ifr in
generic_hwtstamp_get/set_lower(). If ifr is NULL, return
-EOPNOTSUPP to prevent the call to the legacy IOCTL helper.

Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to get/set hwtstamp config")
Closes: https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3
Signed-off-by: Jiaming Zhang <r772577952@gmail.com>
---
 net/core/dev_ioctl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index ad54b12d4b4c..a32e1036f12a 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -474,6 +474,10 @@ int generic_hwtstamp_get_lower(struct net_device *dev,
 		return err;
 	}
 
+	/* Netlink path with unconverted lower driver */
+	if (!kernel_cfg->ifr)
+		return -EOPNOTSUPP;
+
 	/* Legacy path: unconverted lower driver */
 	return generic_hwtstamp_ioctl_lower(dev, SIOCGHWTSTAMP, kernel_cfg);
 }
@@ -498,6 +502,10 @@ int generic_hwtstamp_set_lower(struct net_device *dev,
 		return err;
 	}
 
+	/* Netlink path with unconverted lower driver */
+	if (!kernel_cfg->ifr)
+		return -EOPNOTSUPP;
+
 	/* Legacy path: unconverted lower driver */
 	return generic_hwtstamp_ioctl_lower(dev, SIOCSHWTSTAMP, kernel_cfg);
 }
-- 
2.34.1

Re: [PATCH v2] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()

[kernel test robot]

Hi,

Thanks for your patch.

FYI: kernel test robot notices the stable kernel rule is not satisfied.

The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#option-1

Rule: add the tag "Cc: stable@vger.kernel.org" in the sign-off area to have the patch automatically included in the stable tree.
Subject: [PATCH v2] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Link: https://lore.kernel.org/stable/20251030104942.18561-1-r772577952%40gmail.com

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki